By Jeff Franks
HAVANA (Reuters) - Former Cuban President Fidel Castro lashed out at U.S. President Barack Obama on Thursday for suggesting bilateral relations could improve if Cuba became more democratic, and he said the communist nation would not bow to U.S. pressure.
He also said Obama was being "stupid" over the case of five Cuban agents imprisoned for spying in the United States, who Cuba believes have been treated unjustly.
In his latest opinion column published in Cuba's state-run media, Castro said his country, which is in the midst of economic reforms, will change in the future, but not because of pressure from Obama and the United States, its longtime ideological enemy.
"Many things will change in Cuba, but they will change by our own effort and in spite of the United States. Maybe before that empire falls," he wrote.
Obama said on Wednesday the United States was ready to improve relations with Cuba if the communist-led island embraced democracy and gave its people more freedom.
"If we see positive movement then we will respond in a positive way," Obama said.
"How nice! How intelligent!," Castro said. "So much kindness has not permitted him still to understand that 50 years of blockade and of crimes against our homeland have not been able to break our people."
The Cuban government refers to the five-decade-old U.S. trade embargo against the island as the "blockade."
Castro, 85, complained about the treatment of the five Cuban agents imprisoned in the United States since 1998 and in particular one, Rene Gonzalez, who is set to be released next week after serving his sentence.
U.S. prosecutors have insisted that he remain in the United States for three more years on probation, which Cuba considers unfair. Havana has said he faces danger from anti-Castro Cubans if he does not return to Cuba.
"Such is how the empire responds to the growing global call for the freedom of (the agents)," Castro wrote.
"If it were not that way, the empire would cease to be the empire and Obama would cease being stupid."
Castro has written three columns, or "reflections" as he calls them, this week after writing only one all summer.
He said he is working on a project that has taken precedence over the columns, but his long silence prompted a spate of rumors that his health was failing.
Health problems and age forced Castro to formally cede the Cuban presidency to his younger brother Raul Castro in 2008 after ruling Cuba for 49 years.
On Monday, he described Obama's recent speech to the United Nations General Assembly as "gibberish."
(Editing by Pascal Fletcher and Jackie Frank)